Terminal for circuit breaker switch or the like



June 23, 1964 oc ETAL 3,138,421

TERMINAL FOR CIRCUIT BREAKER SWITCH OR THE LIKE Filed July 51, 1961 /N l/E N TOES R055 5 Lac/15R, 6A 2/.A MD J. DUPLER BY THE/E ATTORNEY-5" HARE/.5, K/EcH, Russsu. & KER/v United States Patent 3,138,421 TERMINAL FOR CIRCUIT BREAIQR SWITCH OR THE LIKE Ross E. Locher, South Pasadena, and Garland J. Duplex,

Canoga Park, Calif assignors to Zinsco Electrical Products, Los Angeies, Calif, a corporation of California Filed July 31, 1961, Ser. No. 128,017 1 Claim. (Cl. 33995) This invention relates to a terminal structure for use in an electrical switch or the like and, in particular, to a releasable terminal structure which does not require any special tools for operation.

Connections in electrical circuits should be tight and firm to Withstand mechanical loads and to have relatively low contact resistance and hence low power loss and low temperature rise at the junction. Permanent connections are ordinarily made by soldering or swaging and present little problem with regard to contact resistance. However, many circuit applications require connections which may be taken apart. Also, in many installations, a permanent connection is diflicult to make and hence connections utilizing a threaded member are employed for applying pressure at the contact surfaces. A screw driver or wrench or other tool is required for tightening and for loosening such a connection.

It is an object of the present invention to provide a releasable connection for an electrical circuit which will have both a strong mechanical engagement and a low resistance electrical engagement. A further object is to provide such a terminal structure in which the connection is made by merely inserting the conductor into the case or other component to which the connection is to be made. Still another object is to provide such a structure in which the conductor may be released by merely applying pressure at an appropriate point on the terminal structure.

It is a particular object of the invention to provide a releasable terminal structure which may be incorporated in conventional switches and circuit breakers permitting installations to be wired and rewired with ease and convenience. A further object is to provide such a terminal structure in which a conductor may be inserted or released with one hand.

It is a specific object of the invention to provide a releasable terminal structure for coupling a conductor to an electrical switch or the like, including a case, an electrically conducting bus bar mounted in the case, and spring means mounted in the case adjacent the bar, with the spring means including an edge section facing the bar for engaging a conductor placed therebetween and urging the conductor into engagement with the bar, and a pressure pad facing the bar for slidingly engaging the conductor and urging the conductor into engagement with the bar. A further object is to provide such a structure including a release member mounted in the case and movable to engage the spring means adjacent the edge section for moving the edge section out of engagement with the conductor permitting the conductor to be slidingly withdrawn from engagement with the pressure pad and bus bar.

It is an object of the invention to provide such a releasable terminal structure incorporating a single spring member having a sharp edge for engaging and holding the conductor in place and a pressure pad for maintaining firm contact between the conductor and the bus bar.

The invention also comprises novel details of construction and novel combinations and arrangements of parts, which will more fully appear in the course of the following description. The drawing merely shows and the description merely describes a preferred embodiment 3,138,421 Patented June 23, 1964 of the present invention which is given by way of illustration or example.

In the drawing:

FIG. 1 is a top plan view showing two circuit breaker switches incorporating the terminal structure of the invention;

FIG. 2 is a side view of the structure of FIG. 1 showing a portion of the cover broken away;

FIG. 3 is a partial sectional view taken along the line 33 of FIG. 2;

FIG. 4 is an enlarged sectional view of a portion of FIG. 2 showing the operation of the terminal structure during disengagement; and

FIGS. 5 and 6 are isometric views of the spring member and release member respectively.

The terminal structure of the invention is illustrated herein as used in a conventional circuit breaker switch such as that shown in the US. Patent No. 2,878,332. Of course, the terminal structure may be incorporated into any type of electrical device but is particularly adapted for use with plug-in switches of the type shown herein.

FIG. 1 illustrates two circuit breaker switches 10, 11, each contained in a case comprising a housing 12 and a cover 13. The switches are designed for side-by-side mounting in a distribution panel, each having a springloaded conductor 14, 15 for engaging a feeder conductor in the panel. Each switch includes a releasable terminal structure, indicated generally at 16, for connecting a typical wire conductor 17 to the switch.

A bus bar 21 of electrical conducting material is mounted in the housing 12 by a screw 22. A spring member 23 is positioned in a spring space 24 in the housing 12. The spring member is preferably formed from a strip of spring steel but of course other resilient materials may be utilized.

The spring member includes a pressure pad 25 positioned adjacent the bus bar 21 and adapted for sliding engagement with the conductor 17. In the preferred form shown herein, one end of the spring member 23 is provided with a convex shape facing the bus bar permitting the conductor to slide in either direction along its axis between the pressure pad and the bus bar.

An edge section is also provided in the spring member for engaging the conductor 17 to permit sliding of the conductor in only one direction. In the preferred embodiment shown herein, the edge section comprises a square-cut end 26 of the spring member positioned adjacent the bus bar 21. This end of the spring member is disposed oblique to the bus bar and slopes away from the end 27 of the conductor. The spring member may be provided with a reverse-bend section 28 for positioning between the wall of the spring space and a boss 29 to maintain the spring in place in the housing.

Means are provided in the terminal structure for releasing the conductor 17 from the edge section 26, permitting the conductor to be slidably withdrawn from the switch housing. In the preferred embodiment described herein, a release member in the form of a bar 32 is positioned in an opening 33 in the housing 12, with a portion of the bar projecting beyond the housing and a portion of the bar projecting into the spring space adjacent the edge section 26. A notch 34 may be provided in the bar for retaining it in place in the housing.

A connection is made to the switch by sliding the conductor 17 into the switch housing through the opening 37. The end 27 of the conductor first engages the edge section 26 of the spring member and then engages the pressure pad 25, pushing each of these portions of the spring member away from the bus bar and passing therebetween to the position shown in FIG. 2. The spring member may be designed to exert a relatively high force at the pressure pad urging the conductor into firm engagement with the bus bar. The spring member also exerts a force on the edge section 26 urging the edge section into engagement with the conductor and urging the conductor into engagement with the bus bar. The terminal structure provides two pressure loads forcing the conductor into contact with the bus bar and hence produces a quite low contact resistance permitting a high current capacity for the connection. The engagement of the edge section 26 with the conductor also produces a force resisting attempts at Withdrawal of the conductor from the housing. Hence it is seen that the spring member meets both the mechanical and electrical connection requirements. While it is noted that the spring member could be made as two independent springs, it is preferred to utilize the single element shown in the drawing for reasons of economy in manufacture and assembly.

The release member bar 32 preferably slides loosely in the opening 33 and takes no part in the making of the electrical connection. When it is desired to remove the conductor from the switch housing, a force is applied to the external end of the bar 32 which pushes the internal end of the bar into engagement with the spring member adjacent the edge section and moves the edge section out of engagement with the conductor, as shown in FIG. 4. The bar 32 is designed so that it does not bite into the conductor and hence provides very little resistance to sliding motion of the conductor. This may be accomplished by rounding the corner 38 or making the bar of a material that is soft relative to the conductor material. Ordinarily, the bar is made of an insulating material for safety reasons. When the bar is pushed inward to the position of FIG. 4, the conductor is easily Withdrawn from engagement with the pressure pad and the connection is released. It should be noted that the bar 32 may be made removable from the housing and only be inserted when it is desired to release a connection. However, it is preferred to provide a release member bar in each switch as shown in the drawing.

The terminal structure of the invention permits the insertion of a conductor into a switch with one motion of one hand, making a satisfactory mechanical and electrical connection. The structure also permits release of the connection with one hand, as by gripping the conductor with the fingers and palm and applying pressure on the release bar with the thumb. The connection may be made and released any number of times without deterioration in the mechanical and electrical qualities thereof. The terminal structure is readily adapted for use in various conventional circuit breakers and switches and meets Underwriters Laboratory requirements for mechanical strength and temperature rise under load.

Although an exemplary embodiment of the invention has been disclosed and discussed, it will be understood that other applications of the invention are possible and that the embodiment disclosed may be subjected to various changes, modifications and substitutions without necessarily departing from the spirit of the invention.

We claim as our invention:

In a releasable terminal structure for coupling a conductor to an electrical switch or the like, the combination of:

a case;

an electrically conducting bus bar mounted in said case, said case having a first opening for receiving a conductor for positioning on said bus bar;

a unitary spring member mounted in said case adjacent said bar, said spring member having inner and outer U-shapes joined at one side, with the free arm of the outer U including an edge section adjacent said first opening and facing said bar for engaging a conductor positioned therebetween and urging said conductor into engagement with said bar, and with the free arm of the inner U including a pressure pad remote from said first opening and facing said bar for slidingly engaging said conductor and urging said conductor into engagement with said bar, said case having a second guide opening aligned with the junction of said edge section and said conductor; and

a releasable member slidably mounted in said second opening and movable to engage the outer U free arm of said spring member adjacent said edge section for moving said edge section out of engagement with said conductor, permitting said conductor to be slidingly withdrawn through said first opening.

References Cited in the file of this patent UNITED STATES PATENTS 1,376,401 Claytor May 3, 1921 2,738,482 Benander Mar. 13, 1956 2,780,791 Morschel Feb. 5, 1957 2,795,677 Slater June 11, 1957 2,944,242 Bentley July 5, 1960 FOREIGN PATENTS 66,719 Norway Sept. 13, 1943 838,778 Germany July 10, 1952 293,258 Switzerland Dec. 1, 1953 544,149 Belgium Jan. 31, 1956 541,182 Canada May 21, 1957 

